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Single instruction, multiple data. Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy.SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it should not be confused with an ISA.
The x86 instruction set has several times been extended with SIMD (Single instruction, multiple data) instruction set extensions.These extensions, starting from the MMX instruction set extension introduced with Pentium MMX in 1997, typically define sets of wide registers and instructions that subdivide these registers into fixed-size lanes and perform a computation for each lane in parallel.
The simplest way to understand SIMT is to imagine a multi-core system, where each core has its own register file, its own ALUs (both SIMD and Scalar) and its own data cache, but that unlike a standard multi-core system which has multiple independent instruction caches and decoders, as well as multiple independent Program Counter registers, the ...
Instructions can be executed sequentially, such as by pipelining, or in parallel by multiple functional units. Flynn's 1972 paper subdivided SIMD down into three further categories: [2] Array processor – These receive the one (same) instruction but each parallel processing unit has its own separate and distinct memory and register file.
MMX had two main problems: it re-used existing x87 floating-point registers making the CPUs unable to work on both floating-point and SIMD data at the same time, and it only worked on integers. SSE floating-point instructions operate on a new independent register set, the XMM registers, and adds a few integer instructions that work on MMX ...
In SIMD the same operation (instruction) is applied on multiple data to manipulate data streams (a version of SIMD is vector processing where the data are organized as vectors). Another class of processors, GPUs encompass multiple SIMD streams processing. Note that SPMD and SIMD are not mutually exclusive; SPMD parallel execution can include ...
SIMD instructions operating on 4 x unsigned bytes or 2 x 16-bit values packed into a 32-bit register (the 64-bit variant of the DSP ASE supports larger vectors, too). SIMD operations are basic arithmetic, shifts and some multiply-accumulate type operations. MIPS SIMD architecture (MSA) Instruction set extensions designed to accelerate multimedia.
Pentium II processor with MMX technology. MMX defines eight processor registers, named MM0 through MM7, and operations that operate on them.Each register is 64 bits wide and can be used to hold either 64-bit integers, or multiple smaller integers in a "packed" format: one instruction can then be applied to two 32-bit integers, four 16-bit integers, or eight 8-bit integers at once.